Novel Universal Testing System for Quantitative Analysis

ABSTRACT

A cassette is disclosed that permits, with an instrument, quantitative analysis to be performed at the moment of sample testing without additional steps to the end user. The cassette includes a calibration strip and a sample strip. The calibration strip contains known quantities of analyte, from which a calibration curve can be created and applied to the analysis of the sample strip. The disclosed cassette can utilize light transmission or light reflectance techniques. The cassette may include a separate wash port for rapid washing of a high background sample. The disclosed cassette may perform diagnostic tests for humans, animals, environmental sample, and/or food samples. In some cases, the disclosed devices and techniques may be used to monitor efficacy of drug therapy and patient compliance with respect to physician-prescribed medication in a point of care setting.

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority from U.S. Provisional Application Ser.No. 62/517,441, filed Jun. 9, 2017, the contents of which areincorporated by reference herein.

BACKGROUND

Blood testing represents a significant majority of human medical testingneeds. Coupled with the growing need for physicians to monitor efficacyof drug therapy, there is also a growing need and demand for a portablequantitative point of care (POC) testing system. POC testing isprojected to reach 22 billion dollars sometime in 2022. Typically, alarge majority of blood tests are done in a central laboratory withexpensive and complicated robotics. In order for many blood tests toreach the POC market the tests will, at a minimum, have to be simple todo and provide the same precision and accuracy as generated by thecentral laboratories. Moderately complex (for example, ELISA) technologyhas allowed physicians to avoid the central laboratory in some cases.However, these technologies are not generally available to ClinicalLaboratory Improvement Amendments (CLIA) licensed POC physicians and aretypically not subject to the Food and Drug Administration (FDA) CLIAwaved status and therefore not available for point of care testing.Previous efforts to provide quantitative point of care testing haverelied on pre-made calibration curves set at the date of manufacture andtransmitted via barcode or chip device sold with the disposable test.However, pre-made calibration curves have significant limitations.

SUMMARY

The disclosed techniques can overcome issues with previously usedtechniques as a sample with an analyte of interest is run concurrentlywith a calibration strip that includes different concentrations of theanalyte of interest being measured in the sample strip or a controlanalyte (i.e., an analyte that is distinct from the analyte ofinterest), while also utilizing the same binding agents. Any minorinstability of the detector binding agent is thus applicable to the samedegree on the construct of the calibration curve and the patient sample.In other words, the disclosed system is self-correcting and capable ofproducing repeatable and accurate results.

Various devices and methods of quantitative and qualitative analysis aredescribed herein. Specifically, a cassette is disclosed that includes an‘on-board’ calibrator. The cassette includes, in many cases, a lateralflow strip for calibration and a lateral flow strip for a sample. Thelateral flow strips are formed of porous membranes which permitcapillary motion of fluid. The “calibration strip” includes at least twoand, in some cases, three, four, or more regions with knownconcentrations of an analyte (either the analyte of interest in thesample or a control analyte). To use the cassette for analysis, a sampleis deposited on the “sample strip” and a chase fluid is supplied to boththe sample strip and the calibration strip. The chase fluid releases aconjugate substance from pads in contact with the sample strip and thecalibration strip and the conjugate substance then travels up thestrips. The conjugate substance is a binding partner to the analyte ofinterest and may comprise or consist of a marker. On the calibrationstrip, the conjugate substance encounters and binds with the analytepresent. Once bound to the analyte (either directly or indirectly via adistinct binding partner), the marker emits a signal, which is directlyproportional to the amount of analyte present. The signals that developon the calibration strip are then interpreted optically by an instrumentto generate a calibration curve which is used to calculate or interpretthe concurrent signal that develops on the sample strip. The disclosedcassettes may be compatible with an instrument capable of interpretingimages either through light transmission or light reflectance. Inembodiments where increased sensitivity is desired, light transmissioncan be used.

The disclosed cassettes can be configured to measure any desired analyteof interest. For example, the cassettes can be configured to measureantigens, antibodies, hormones, proteins, receptors, DNA, RNA, enzymes,pharmaceutical substances, and/or environmental pollutants. Appropriatebinding partners and/or markers can be selected based on the selectedanalyte of interest and/or control analyte and used to create anappropriate calibration strip and sample strip.

In one particular example embodiment, a cassette is designed to measurean antigen of interest. The calibration strip for this cassette includesknown concentrations of the antigen and an antibody immunologicallybound to the antigen. In this example embodiment, the cassette includesa conjugate pad with marker (for example, gold particles). When chasefluid is introduced, the marker is reconstituted and travels to and bindwith the antigen bound to the antibody. On the sample strip, the samplemixes and together with the chase fluid reconstitutes the marker (inthis example, colloidal gold detector particles) and moves onto a porousmembrane. If antigen is present, a signal develops.

In a different example embodiment, a cassette is designed to measure anantigen of interest and the calibration strip includes knownconcentrations of an antigen bound to a marker. In this exampleembodiment, the conjugate pad includes antibodies which travel to andbind with the antigen bound to the marker when chase fluid isintroduced. The cassettes disclosed herein may include a calibrationstrip and a sample strip with numerous possible combinations of suitablebinding partners and/or markers for particular analytes of interest.Although antibodies and antigens are discussed in detail, the subjectdisclosure is not intended to be so limited. For example, sample andcalibration strips that include analytes such as hormones, proteins,vitamins, enzymes, DNA, RNA, pharmaceutical substances, and/orenvironmental pollutants are all within the scope of the subjectdisclosure.

Surprisingly, the disclosed cassettes with “on-board” calibrationfeatures are able to distribute fluid, sample, binding agents and/ormarkers up two lateral flow strips evenly and with inconsequentialvariation. Furthermore, the disclosed cassettes are able to produce arobust and stable calibration curve from the calibration strip andaccurately report an unknown quantitative result from the sample strip.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a perspective view of an exemplary cassette that includes acalibration strip and a sample strip, in accordance with someembodiments of the subject disclosure.

FIG. 2 shows an exploded view of the exemplary cassette shown in FIG. 1,in accordance with some embodiments of the subject disclosure.

FIG. 3 shows a bottom view of an exemplary cassette shown in FIG. 1, inaccordance with some embodiments of the subject disclosure.

FIG. 4 shows a top view of the bottom portion of an exemplary cassettehousing shown in FIG. 1, in accordance with an embodiment of the subjectdisclosure.

FIG. 5 shows an inside view of the top portion of an exemplary cassettehousing shown in FIG. 1, in accordance with an embodiment of the subjectdisclosure.

FIG. 6 shows a perspective view of an exemplary calibration stripconfigured in accordance with some embodiments of the subjectdisclosure.

FIG. 7 shows a perspective view of an exemplary sample strip configuredin accordance with some embodiments of the subject disclosure.

FIG. 8 shows a graphical representation of quantitative results obtainedusing an on-board calibrator for measuring Respiratory Syncytial Virus(RSV), in accordance with some example embodiments.

FIG. 9 shows a graphical representation of quantitative kinetic resultsobtained using an on-board calibrator for measuring thyroid stimulatinghormone (TSH) at a concentration of 57.5 μIU/ml, in accordance with someexample embodiments.

FIG. 10 shows a graphical representation of quantitative kinetic resultsobtained using an on-board calibrator for measuring TSH at aconcentration of 5.75 μIU/ml, in accordance with some exampleembodiments.

FIG. 11 shows a graphical representation of quantitative kinetic resultsobtained using an on-board calibrator for measuring TSH at aconcentration of 0.575 μIU/ml, in accordance with some exampleembodiments.

FIG. 12 shows a graphical representation of pixel area measured from anexample cassette formed in accordance with some example embodiments, asa function of sample volume.

FIG. 13 shows a graphical representation of quantitative resultsobtained using an on-board calibrator for measuring Histoplasmacapsulatum, in accordance with some example embodiments.

DETAILED DESCRIPTION

Testing devices, namely cassettes, are disclosed that provide “on-board”calibration functionality. In particular, the disclosed cassettesinclude a calibration strip and a sample strip, each formed of a porousmaterial that permits fluid to flow therethrough using capillary force.The calibration strip contains known quantities of analyte, from which acalibration curve can be created and applied to the analysis of thesample strip. The cassette may include a separate wash port for rapidwashing of a high background sample.

The cassette produces a signal, which can be read using lighttransmission or light reflectance techniques. The disclosed cassettescan be used in diagnostic tests for humans, animals, environmentalsample, and/or food samples. If desired, the disclosed devices andtechniques may be used to monitor efficacy of drug therapy and/orpatient compliance with respect to physician-prescribed medication in apoint of care (POC) setting. Details regarding construction of thecassette, calibration strip, and sample strip are described below indetail, along with related methods of use.

Cassette

FIG. 1 shows a perspective view of an example cassette 100 that includesa calibration strip 7 and a sample strip 2, in accordance with someexample embodiments. As shown in FIG. 1, cassette 100 includes asubstantially rigid housing having a top portion 1 and a bottom portion8. Top portion 1 and bottom portion 8 of the housing may, in someembodiments, interconnect upon being pushed together to form a press fitor friction fit and remain mechanically secured together withoutadhesives. In some embodiments, top housing 1 and bottom housing 8 mayinclude clamping regions 6 designed to form a press fit with theopposing housing. In some embodiments, cassette 100 includes at leastone, at least, two, at least three, at least four, at least five, or atleast six clamping regions 6.

FIG. 1 illustrates a cassette 100 with a sample strip 2 and acalibration strip 7. Within the cassette 100, fluid port 5 contacts bothsample strip 2 and calibration strip 7. Cassette 100 also includes asample port 4 into which sample can be introduced before travelingthrough sample strip 2. Sample port 4 is not in fluid communication withcalibration strip 7. In some embodiments, cassette 100 includes a washport 3, which may be used to provide additional wash for high backgroundsamples (for example, hemolyzed blood or pigmented samples). Whenpresent, wash port 3 is in fluid communication with sample strip 2 butnot necessarily in fluid communication with calibration strip 7.

FIG. 2 shows an exploded view of the exemplary cassette 100 shown inFIG. 1. In particular, fluid pad 5, calibration strip 7, and samplestrip 2 are more clearly visible and features of clamping regions 6 areshown. For example, FIG. 2 shows an example embodiment where the bottomportion 8 of the housing includes two arms 6A that clamp ontocorresponding recessed areas 6B of the top portion 1 of the housing. Inthe example embodiment shown in FIG. 2, the top portion 1 of the housingincludes four arms 6C that clamp onto corresponding recessed areas 6D ofthe bottom portion 8 of the housing.

FIG. 3 shows a bottom view of the exemplary cassette 100 shown inFIG. 1. As shown in FIG. 3, the bottom portion 8 of the housing mayinclude a positioning groove 9, which allows the cassette 100 to beeasily positioned for reading and analysis. The bottom portion 8 of thehousing may also include a flow strip light guide port 10 positionedunderneath the calibration strip 7, which may be used fortransmission-based detection methods. In some example embodiments, abarcode 11 may be placed on cassette 100, as shown in FIG. 3. A samplevolume analysis port 12 may also be included in the bottom portion 8 ofthe housing underneath the sample strip 2. In some embodiments, thebottom portion 8 of the housing may also include a flow strip lightguide port 13 positioned underneath the sample strip 2 fortransmission-based detection methods.

FIG. 4 shows a top view of the bottom portion 8 of an exemplary cassettehousing. As illustrated in FIG. 4, bottom portion 8 of the cassettehousing includes flow strip light guide port 10, sample volume analysisport 12, flow strip light guide port 13, and one or more clampingregions 6. Additionally, the bottom portion 8 of the housing may alsoinclude a plurality of excess fluid channels 14 to remove excess liquidfrom the flow strips. Excess fluid channels 14 may be positioned on oneor more sides of the flow strips, as shown in FIG. 4. In some exampleembodiments, excess fluid channels 14 may be formed between flow strips2 and 7 (shown in FIG. 2). In these and other embodiments, excess fluidchannels 14, at times also referred to as “capillary disruptors,” may beformed on inner and/or outer sides of the sample strip 2 and/or thecalibration strip 7 (shown in FIG. 2), as shown in FIG. 4. FIG. 4 showsan example cassette housing with capillary disruptors 14 formed on bothinner and outer sides of sample strip 2 and calibration strip 7.

The bottom portion 8 of the cassette housing may also include side walls15, which surround strips 2 and 7 (shown in FIG. 2). In someembodiments, side walls 15 may be lower in some regions to permit fluidfrom a flow strip (for example, a sample strip or calibration strip) toenter an excess fluid channel 14. In these and other embodiments, afluid pad positioning bar 16 may also be formed in bottom portion 8 ofthe housing to facilitate proper positioning of a fluid pad.

FIG. 5 shows an inside view of the top portion 1 of an exemplarycassette housing. As shown, top portion 1 includes a fluid pad port 17that provides fluid communication to both the sample strip 2 and thecalibration strip 7 (shown in FIG. 2). Top portion 1 also includes asample port 4 to allow sample to be introduced to a sample strip. Insome embodiments, top portion 1 is configured to include a plurality ofraised regions (referred to herein as “pressure points”) that exertpressure on the sample strip 2 and/or the calibration strip 7.

In some embodiments, top portion 1 includes a plurality of pressurepoints 18, with an equal number of pressure points 18 in contact withsample strip 2 and calibration strip 7. FIG. 5 shows an exampleembodiment of the top portion 1 of the cassette that includes aplurality of pressure points 18. For example, pressure points 18 acontact the sample strip 2 and pressure points 18 b contact thecalibration strip 7. Pressure point 18 c surrounds wash port 3 abovesample strip 2. In the example embodiment shown in FIG. 5, calibrationstrip 7 includes a pressure point 18 d in the same shape as pressurepoint 18 c, although no wash port is provided underneath. Havingmatching pressure points on both the calibration strip and sample stripcan ensure that lateral flow progresses the same on both strips and themeasurements obtained from the strips are comparable. Pressure points 18e are in contact with the sample strip 2 and pressure points 18 f are incontact with calibration strip 7. To match the contact provided by apressure point 18 g surrounding sample port 4, top portion 1 of thehousing may also include pressure point 18 h, although no port ispresent in that location. As shown in FIG. 5, a pressure point 18 i maybe provided surrounding fluid pad port 17 that contacts both samplestrip 2 and calibration strip 7.

FIG. 5 illustrates a cassette having seventeen pressure points (18 a-18i), but it will be understood upon consideration of the subjectdisclosure that some example cassettes may include more or less pressurepoints than shown in FIG. 5. For example, in some embodiments, the topportion 1 of the cassette housing may include at least two, three, four,five, six, seven, or eight pressure points on each flow strip. In total,the top portion 1 of the housing may include any number of pressurepoints. For example, the top portion 1 may include between 2 and 30pressure points, 5-25, or 10-20 pressure points. The example embodimentshown in FIG. 5 includes 17 pressure points, but embodiments with moreor less pressure points are within the scope of the present disclosure.In various embodiments, at least one pressure point contacts both samplestrip 2 and calibration strip 7. Additionally, the pressure pointsincluded on the top portion 1 of the cassette housing may be shaped asshown in FIG. 5, with linear, square, circular, and oval shapes, while,in other embodiments, other various other shapes or arrangements ofshapes may be used.

Calibration Strip

FIG. 6 shows an exemplary calibration strip 7. The calibration strip 7shown in FIG. 6 includes various substrates that permit capillary motionof fluid, affixed to an adhesive-lined backing 102. In some embodiments,backing 102 is formed of a polymeric material that is approximately aslong as the calibration strip 7. In select embodiments, backing 102 isoptically clear. In particular, backing 102 may permit transmission ofat least 95% of visible light. A capillary flow substrate 104 may thenbe adhered to backing 102. Capillary flow substrate 104 may be formed ofany suitable material, such as nitrocellulose or another porous materialthat permits fluid to flow via capillary action, such as nylon orpolystyrene. In some embodiments, capillary flow substrate 104 extendsalong the entire length of backing 102 while in other embodiments,capillary flow substrate 104 is shorter than backing 102.

The capillary flow substrate 104 of calibration strip 7 may includemarker regions 106 that include known concentrations of an analyte, abinding partner for the analyte, and/or a marker which, when bound tothe analyte or to a binding partner bound to the analyte, emits adetectable signal. In some embodiments, the analyte on the calibrationstrip 7 is the same as the analyte of interest in the sample, while inother embodiments, the analyte on the calibration strip 7 is a controlanalyte that is distinct from the analyte of interest in the sample. Inembodiments where a control analyte is used, the control analyte may bean analyte that binds to the same binding agents as the analyte ofinterest. The marker regions 106 may include appropriate componentsbased on the design on the assay employed for the testing device. Forexample, if an example assay is designed to detect an antigen (as theanalyte of interest), the assay may use an antibody as the bindingpartner and a gold particle as the marker. In some such embodiments, themarker regions 106 may include known quantities of antigen bound toantibody or known quantities of antigen and gold particles. Inembodiments where the marker regions 106 include antigen bound toantibody, the gold particles may be included in a conjugate pad 110 andtravel upwards to the marker regions 106 during the assay. Once the goldparticles encounter the antigen bound to antibody, they may bond to forma complex. In embodiments where the marker regions 106 include antigenand gold particles, the conjugate pad 110 may include antibodies whichtravel upwards to the marker regions 106 during the assay and form acomplex with the antigen and gold particles.

Numerous configurations and variations of the assay employed by thedisclosed testing device are possible. For example, in some embodiments,the analyte of interest may be a receptor, hormone, antigen, antibody,protein, enzyme, DNA, RNA, vitamin, pharmaceutical substance, and/orenvironmental pollutant. In such cases, a suitable binding partner canbe selected based on the identity of the analyte of interest. Forexample, suitable binding partners may be organic compounds, inorganiccompounds, receptors, antigens, antibodies, hormones, enzymes, proteins,and/or DNA. Example markers beyond colloidal gold that may be used tobind to the analyte of interest directly or indirectly include but arenot limited to: enzymes (such as horseradish peroxidase, alkalinephosphatase, or glucose oxidase), selenium, radioactive isotopes, DNAreporters, fluorogenic reporters (such as phycoerythrin), and/or electrochemiluminescent tags, inorganic compounds, such as silicon dioxide,ferric oxides, and chemical derivatives of inorganic compounds.

Additionally, the assay of the disclosed testing device may becompetitive or non-competitive and may include one, two, or more bindingsites. For example, the assay may be a one-site non-competitive assay inwhich the analyte binds with a marked binding partner (for example, alabelled antibody) and signal from the marked binding partners ismeasured to determine the concentration of analyte. In otherembodiments, the assay may be a two-site non-competitive assay in whichanalyte binds to both a first binding partner (for example, an antibodysite) and a marked binding partner (for example, a labelled antibody).This type of assay is commonly known as a “sandwich assay.” In otherembodiments, the assay may be a competitive assay, in which unmarkedanalyte competes with marked analyte to bind to a binding partner (forexample, an antibody). The amount of marked, unbound analyte is thenmeasured and used to calculate the concentration of (originallyunmarked) analyte in the sample.

The example calibration strip 7 shown in FIG. 6 includes four distinctmarker regions 106, but other embodiments may include at least two, atleast three, four, five, or more marker regions 106. In someembodiments, the distinct marker regions 106 are each non-zero, while inother embodiments, at least one distinct marker region is zero. Forexample, in one embodiment, calibration strip 7 may include two distinctmarker regions, with one being zero and the other being non-zero. Inanother example embodiment, calibration strip 7 may include two non-zerodistinct marker regions. The marker regions 106 may be horizontal lines,as shown in FIG. 6, or may be non-linear. In some embodiments, eachmarker region 106 includes a different concentration of analyte and/orbinding partner. In other embodiments, however, two of the markerregions 106 may include the same concentration of analyte and/or bindingpartner to evaluate deviations in measurement. For example, in someembodiments, the marker region 106 of a calibration strip includesanalyte (with or without binding partner) in a concentration range ofbetween 0 and 100%. In some embodiments, the marker region 106 of acalibration strip includes analyte concentrations that vary by more than5%, more than 20%, or more than 50%. In one particular exampleembodiment, a calibration strip includes a first region with analyte ina concentration of 40%, a second region with analyte in a concentrationof 60%, a third region with analyte in a concentration of 80%, and afourth region with analyte in a concentration of 100%. In someembodiments, marker regions 106 may be arranged on calibration strip 7such that fluid encounters regions with a lower analyte concentrationprior to regions with a higher analyte concentration. Conversely, markerregions may be arranged such that fluid encounters regions with higheranalyte concentration prior to regions with lower analyte concentration.Numerous configurations and variations will be apparent in light of theteachings provided herein.

As shown in FIG. 6, calibration strip 7 includes a conjugate pad 110,which is in contact with capillary flow substrate 104. In someembodiments, conjugate pad 110 may be positioned at least partiallyunderneath or at least partially overlaying capillary flow substrate104. Conjugate pad 110 may be formed of nitrocellulose or another porousmaterial. In some embodiments, conjugate pad 110 may be loaded withappropriate materials for the assay, such as binding partners for theanalyte of interest and/or markers. In some particular exampleembodiments, the conjugate pad contains dried detector antibodies boundto gold particles. When chase fluid is added via the fluid port 5 of thecassette 100, the fluid flows to both the calibration strip 7 and thesample strip 2, and the assay begins. The chase fluid may be anysuitable fluid, such as water (for example, deionized water). In selectembodiments, the chase fluid may include one or more buffers. The chasefluid mobiles or reconstitutes the compound(s) loaded on the conjugatepad 110. For example, if the conjugate pad includes dried detectorantibodies bound to gold particles, the chase fluid will reconstitutethe gold labeled detector antibody before continuing to flow up thecapillary flow substrate 104. When the reconstituted gold labeleddetector antibody reaches the antigen on the calibration strip, it bindsto the antibody-antigen and forms a complex(antibody-antigen-Au-antibody), which produces signal.

In some embodiments, a sample pad 112 may be positioned on thecalibration strip 7 at least partially overlapping conjugate pad 110.Sample pad 112 may be implemented with any appropriate material, such asnitrocellulose or another porous material. As described below in detail,sample strip 2 includes a sample pad onto which sample is deposited. Inembodiments where sample strip includes a distinct sample pad,calibration strip 7 may also include a similarly-sized sample pad 112,as shown in FIG. 6.

Additionally, calibration strip 7 may also include an absorbent pad 108,as shown in FIG. 6, to collect excess fluid. Absorbent pad 108 overlapscapillary flow substrate 104 and may be formed of an absorbent material,such as nitrocellulose or other porous material. In some embodiments,one or more pressure points 18 on the top portion 1 of the cassettehousing may be in contact with absorbent pad 108.

As will be understood by those skilled in the art upon consideration ofthe subject disclosure, calibration strip 7 may include fewer or moredistinct portions than those shown in FIG. 6. In particular, FIG. 6illustrates a calibration strip 7 that includes separate and distinctporous members for sample pad 112, conjugate pad 110, absorbent pad 108,and capillary flow substrate 104. However, in some embodiments,calibration strip 7 may be formed with fewer distinct porous members.For example, in some embodiments, calibration strip 7 may be formed witha single unitary porous member that includes regions corresponding tosample pad 112, conjugate pad 110, absorbent pad 108 and/or capillaryflow substrate 104, in some embodiments. Numerous configurations andvariations will be apparent to those skilled in the art.

Sample Strip

FIG. 7 illustrates an example sample strip 2 that includes backing 202,which may be the same or different from backing 102 of calibration strip7, capillary flow substrate 204, which may be the same or different fromcapillary flow substrate 104, and absorbent pad 208, which may be thesame or different from absorbent pad 108. In some circumstances, it maybe advantageous to use the same materials in both the calibration stripand sample strip for the backing, capillary flow substrate, andabsorbent pad to promote uniformity between the strips and ensuresimilar assay conditions. Sample strip 2 also includes a conjugate pad210, which may be configured as described with respect to conjugate pad110, and sample pad 212, which may be configured as described withrespect to sample pad 112. In some embodiments, the material used forsample pad 112 of the calibrator strip 7 is the same material used forsample pad 212 of the sample strip 2.

As shown in FIG. 7, the sample strip 2 may include a test line 214 and acontrol line 216. Sample strip 2 may be configured such that fluidencounters test line 214 prior to control line 216 (as shown in FIG. 7)or such that fluid encounters control line 216 prior to test line 214.In some embodiments, control line 216 includes a known quantity ofanalyte (either analyte of interest or a control analyte) and the testline 214 includes one or more binding partners for the analyte ofinterest. In some embodiments, control line 216 may also include abinding partner for the analyte and/or a marker. For example, in oneparticular embodiment, the analyte of interest is an antigen and controlline 216 includes known quantities of the antigen bound to an antibody.In this example embodiment, test line 214 also includes an antibody thatwill bind to analyte in the sample. The assay for this example cassetteis performed using marker particles that travel from the conjugate padand bind with the analyte complexes formed on the sample strip 2. In adifferent example embodiment, control line 216 includes known quantitiesof analyte and a marker. In this example embodiment, test line 214includes marker particles and the assay is performed when the antibodybinding partner travels to the test line 214 and control line 216 fromthe conjugate pad. Numerous variations for control line 216 and testline 214 will be apparent to one skilled in the art upon considerationof the subject disclosure.

Working Example 1

In a first example embodiment, a cassette includes a sample strip and acalibration strip designed to quantitatively test for RespiratorySyncytial Virus (RSV). The common lateral flow architecture for thesample strip and the calibration strip is as follows.

An example lateral flow strip was constructed using Lohmann Corporationadhesive backing plastic (0.010″ White or clear polyester laminated withGL-187® acrylic PSA & supported with a release liner). Sartorius 25 mmCN140 Nitrocellulose was placed on top of the Lohmann backing materialapproximately 37 mm from the bottom of the backing material. 22 mm wideabsorbent pad material CF5 from Whatman/GE was indexed with the top ofthe Lohmann backing material, creating an overlap onto thenitrocellulose and corresponding with pressure points of the cassettehousing. On the lower side of the nitrocellulose a conjugate padmaterial is placed (14 mm Ahlstrom 6614, and/or Ahlstrom 1281 placed sothat it creates an overlap on top of the nitrocellulose). A final 24 mmsample application material is indexed to the bottom of the Lohmannbacking material to create an overlap onto the conjugate pad material.Once all components were assembled, the laminated material was then cutinto 6 mm wide strips using a Biodot guillotine cutter. Additionally, a10×15 mm fluid pad made from Ahlstrom 6614 was cut and placed over thebottom of the strips. To immunologically bind antigen, nitrocellulose isused to bind antibodies directed against the antigen of interest in therange of 50 pg/ml-3 mg/ml. A Biodot dispensing platform was used toaccurately dispense four lines of antibody. The nitrocellulose wassubsequently dried under forced hot air. With a second pass through theBiodot dispensing platform, antigen was dispensed on top of the antibodyand subsequently dried. To create the increasing signal intensityladder, increasing amounts of antigen (ng/mL) was used per line (lowestat the bottom). Detector antibody bound to gold particles from the samelot and concentration as the sample strip is applied to the conjugatepad material and dried.

The sample strip was constructed by depositing monoclonal anti RSV fromVirostat Inc at 1.5 mg/mL onto Sartorius CN140 nitrocellulose using aBiodot dispensing system at a rate of 1 uL/cm. A goat anti chickencontrol line at 0.5 mg/mL was also deposited north of the RSV line at arate of 1 uL/cm. Ahlstrom 1281 overlapped onto the nitrocellulose andAhlstrom 6614 served as the sample/conjugate pad. A solution containinganti RSV from Virostat Inc conjugated to BBI 60 nm colloidal goldparticles, and chicken IgY conjugated to BBI 40 nm colloidal goldparticles were sprayed down onto the Ahlstrom 6614 using the Biodotdispensing system at a rate of 15 uL/cm and dried. Once laminated ontothe Lohmann backing material, these strips were cut to 6 mm wide usingthe biodot cutter.

The calibration strip of this example embodiment was constructed asfollows. Monoclonal anti RSV from Virostat Inc at 1.5 mg/mL wasdeposited into four evenly spaced lines onto Sartorius CN140nitrocellulose using the Biodot dispensing platform and dried. With asecond pass on the biodot dispensing platform, dilutions of RSV antigenpositive control from Zeptometrix (40% on line 1, 60% on line 2, 80% online 3 and 100% on line four) were deposited on top of the antibodylines and dried.

A chase fluid for the RSV reagents was prepared using Triton x 100, Trisbuffer and Proclin 300. This solution was added to the fluid entry portafter the sample was added.

The described calibration and sample strips were assembled into acassette along with a fluid pad. 20 uL of patient sample prepared from anasal swab, nasal pharyngeal swab, nasal wash or viral transport mediawas added to the sample entry port. 300 uL of chase fluid was added tothe fluid entry port. The cassette was then allowed to react at roomtemperature for 10 min. Signals from the four calibration lines on thecalibration strip were recorded using a light reflectance lateral flowreader system from Detekt Biomedical and compared against unknownsignals generated from the sample strip. Each cassette received its owncalibration calculated from signals generated at the 10 min time point.Data obtained from this example was then compared to standards(dilutions of a positive control) to determine the accuracy of thecassette devices. Table 1 shows the results obtained. FIG. 8 shows agraphical representation of the results obtained using an on-boardcalibrator for measuring RSV.

TABLE 1 Accuracy of On-Board Calibrator for Measuring RSV Actual RSVMeasured RSV Concentration Concentration Difference % Difference  0%−.035% 0.35% N/A  5% 4.99% 0.01% 0.20% 10% 10.52% 0.52% 5.19% 25% 23.30%1.70% 6.8% 50% 51.70% 1.70% 3.4% 100%  100.90% 0.90% 0.90%

As shown in Table 1, the example testing device accurately predicted thepercentage dilution of the positive control solution. Additionally, thelargest difference recorded was less than a 7% error in measurement. Insome embodiments, the quantitative measurement of the analyteconcentration in the sample has an error percentage of less than 5%, 4%,3%, 2%, or 1%.

Working Example 2

In another example embodiment, a kinetic lateral flow test was createdto detect human thyroid stimulating hormone (TSH) levels in whole blood.The example testing device was constructed according to the followingprocedure. The calibration strip and sample strip were producedaccording to the common lateral flow architecture described in workingexample 1.

The sample strip was created by depositing monoclonal anti TSH(Biospacific) at 2 mg/mL onto 28 mm Sartorius CN140 nitrocellulose usinga Biodot dispensing system at a rate of 1 uL/cm. A goat anti chickencontrol line at 0.5 mg/mL was also deposited north of the TSH line at arate of 1 uL/cm. Ahlstrom 6614 (14 mm) overlapped the nitrocellulose andserved as the conjugate pad material. A solution containing monoclonalanti TSH (Biospacific) conjugated to BBI 60 nm colloidal gold particlesand chicken IgY conjugated to BBI 40 nm colloidal gold particles weresprayed down onto the Ahlstrom 6614 using the Biodot dispensing systemat a rate of 15 uL/cm and dried. Once laminated onto the Lohmann backingmaterial, these strips were cut to 6 mm wide using the Biodot cutter.

The calibration strip was constructed by depositing four evenly spacedlines of the same antibody and concentration used for the sample striponto Sartorius CN140 nitrocellulose using the Biodot dispensing platformand dried. With a second pass on the biodot dispensing platform, TSHfrom Scripps Laboratories diluted into TSH free human serum (3.6 ng online 1, 0.36 ng on line 2, 0.036 ng on line 3 and 0.0036 ng on linefour) was deposited on top of the antibody lines and dried.

A chase fluid was developed to be compatible with the TSH reagents andto limit blood hemolysis. The chase fluid solution incorporated Tween20, Sodium bicarbonate, and EDTA. This solution was added to the fluidentry port after the sample was introduced.

The example calibration and sample strips were assembled into thecassette along with a fluid pad. 20 uL of patient sample was added tothe sample entry port and 200 uL of assay run fluid was added to thefluid entry port.

The cassette was then inserted into a light transmission instrument(OIDx) which was capable of kinetically analyzing the cassette overtime. Signals from the four calibration lines were recorded and comparedagainst unknown signals generated from the sample. Each cassettereceived its own calibration calculated from signals generated atvarious time points. To determine the accuracy of the on-boardcalibration system, known standards were run as samples (Dilutions ofWorld Health TSH standard). FIG. 9 shows the calculated concentrationcompared to the actual concentration as a function of assay time for the57.5 μIU/ml sample and FIG. 10 shows the calculated concentrationcompared to the actual concentration as a function of assay time for the5.75 μIU/ml sample.

As shown in FIG. 11, the 0.575 μIU/TSH sample, the value is reachedwithin three minutes. In other embodiments, a lower standard of 0.0575μIU/ml is used with similar results. By incorporating an assay stopfunction using accumulated signal on a control line, either located onthe sample strip or the calibration strip, kinetic assays can bedesigned to produce values at the limit of detection (LOD) of an assay.For example, in the experiment above, if the LOD is 0.575 μIU/ml, theassay would be completed in three minutes. In some example embodiments,the LOD may be as low as 0.1 μIU/ml or 0.05 μI/ml. In some embodiments,the devices described herein are able to detect analyte at its LOD, forexample, a concentration of 0.05 μIU/ml or less, within ten minutesafter the chase fluid is introduced.

Working Example 3

In another example embodiment, a cassette was designed to detect humanTSH levels in whole blood, which can cause background staining when usedas a sample. The light transmission and sample volume analysis were alsoassessed. The calibration strip and sample strip were produced accordingto the common lateral flow architecture described in working example 1.The example cassette was constructed as follows.

The sample strip was prepared by depositing monoclonal antiTSH(Biospacific) at 2 mg/mL onto 28 mm Sartorius CN140 nitrocelluloseusing a Biodot dispensing system at a rate of 1 uL/cm. A goat antichicken control line at 0.5 mg/mL was also deposited north of the TSHline at a rate of 1 uL/cm. Ahlstrom 6614 (14 mm) overlapped thenitrocellulose and served as the conjugate pad material. A solutioncontaining monoclonal anti TSH(Biospacific) conjugated to BBI 60 nmcolloidal gold particles and chicken IgY conjugated to BBI 40 nmcolloidal gold particles were sprayed down onto the Ahlstrom 6614 usingthe Biodot dispensing system at a rate of 15 uL/cm and dried. Oncelaminated onto the Lohmann backing material, these strips were cut to 6mm wide using the Biodot cutter.

Chase fluid was developed to be compatible with the TSH reagents and tolimit blood hemolysis. The chase fluid solution incorporated Tween 20,Sodium bicarbonate, and EDTA. This solution was added to the fluid entryport after the sample was introduced. 25 uL of a highly hemolyzed wholeblood sample was added to the sample port and then tested as normal. Atnine minutes into the assay, the cassette was visually evaluated forproblems due to hemolysis. Table 2 describes what was observed and howthe wash port was used to clear up the background.

TABLE 2 Experimental Technique for Utilizing Wash Port Time (minutes)Background Quality (after 9 min) Treatment 9:00 Poor, red background 10uL of push buffer into the wash port 9:10 Immediate clearing at bottomof Additional 10 uL of push viewing window buffer into the wash port9:20 White background ⅓ up the strip Additional 10 uL of push bufferinto the wash port 9:30 White background over the test Additional 10 uLof push line buffer into the wash port 9:40 White background over thecontrol Additional 10 uL of push line buffer into the wash port 9:50White background over ¾ of strip Additional 10 uL of push buffer intothe wash port 10:00  White background over entire strip Test read

As shown in this example embodiment, the wash port can provide aneffective way of clearing high background samples. Furthermore, the washport is also amenable to automated practices. For example, in someembodiments, a cassette may be configured to automatically apply asolution via the wash port when background noise of a certain signalintensity is detected. Numerous implementation techniques will beapparent to one skilled in the art upon consideration of the subjectdisclosure.

Working Example 4

In another example embodiment, an instrument was created to measurelight transmission and sample volume. This example instrument isreferred to as “OIDx” herein. The OIDx instrument was programmed tomeasure pixel area from an image. To program the instrument, variousamounts of whole blood were added to the sample port of an examplecassette. An image of the strip was captured 30 seconds after the wholeblood was added. FIG. 12 shows a graph of the signal measured (based onpixel area) as a function of the sample volume.

As can be seen in FIG. 12, the measured pixel area is linear between 14μL and 26 μL of sample volume. The example light transmission instrumentmay, in some embodiments, eliminate the need to use a pipette fortransferring sample volumes, such as blood from a finger prick. This mayreduce further manipulative steps in the test procedure, therebyincreasing the likelihood of obtaining CLIA-waved status by the FDA.

Working Example 5

In another example embodiment, a cassette was created to detecthistoplasma in urine. The sample strip for the cassette was constructedusing the common lateral flow architecture as previously described. Tocreate the sample strip, rabbit monoclonal anti Histoplasma Capsulatumat 1.5 mg/mL was deposited onto 25 mm Sartorius CN140 nitrocelluloseusing a Biodot dispensing system at a rate of 1 uL/cm. A goat antichicken control line at 0.5 mg/mL was also deposited north of theanti-Histoplasma line at a rate of 1 uL/cm. Ahlstrom 6614 overlapped thenitrocellulose and served as both the conjugate and sample pad. TheAhlstrom 6614 was treated prior to the depositing of colloidal gold toreduce interference with urine samples. A solution containing antiHistoplasma cap. conjugated to IMRA 40 nm colloidal gold particles andchicken IgY conjugated to IMRA 40 nm colloidal gold particles weresprayed down onto the Ahlstrom 6614 using the Biodot dispensing systemat a rate of 15 uL/cm and dried. Once laminated onto the Lohmann backingmaterial, these strips were cut to 6 mm wide using the Biodot cutter.

A chase fluid was developed to be compatible with the Histoplasmareagents and to limit interference from urine samples. The chase fluidsolution incorporated Sodium Dodecyl Sulfate, Sodium Citrate andphosphate buffer. The described strip was placed into the cassette alongwith a fluid pad.

60 uL of urine spiked with known concentrations of Histoplasmacapsulatum was added to the sample port. 300 uL of chase fluid was addedto the fluid port and the assay was run for 10 minutes. Results wereread on a Detekt Biomedical reader to quantitate signal. The dataobtained is shown in FIG. 13. The data shown in FIG. 13 indicates thatHistoplasma capsulatum can be detected in urine using the methods anddevices described herein.

Additional Example Embodiments

The following additional example embodiments are provided to describeaspects of the presently disclosed methods and devices in further detailand are not intended to limit the scope of the subject disclosure.

In some example embodiments, a universal method for quantitative sampleanalysis is provided. The method may include, in some cases, acalibration curve obtained simultaneously with the sample analysiswithout additional user steps. In these and other embodiments, a lateralflow-based system can be achieved, where sample is added to an absorbentmaterial which together with chase fluid reconstitutes dried colloidalgold antibody detector conjugates or other suitable detector bindingagents. Through capillary force, the sample and colloidal gold detectormoves laterally onto a controlled porosity membrane where bindingpartners such as antibodies, antigens, receptors and the like have beenpreviously adsorbed onto the membrane. If analyte, i.e. antigen orantibody is present in the sample, a reaction occurs between thespecific binding agents to produce a signal that can be read visually orquantitatively with an instrument and a calibration curve. This iscommonly referred to as a ‘sandwich assay,’ where the analyte ofinterest is sandwiched between two suitable binding partners, one ofwhich has a detector signal associated with the binding agent. Thesignal is directly proportional to the analyte concentration. In theseand other embodiments, signals on the calibrator strip, which developconcurrent with the sample strip, are interpreted by an instrument tocreate a calibration or standard curve that the sample is compared to,thereby generating a quantitative result for the sample.

Techniques for creating a calibration curve (sometimes referred to as a‘standard curve’) from measured signals are known to those skilled inthe art. For example, measured signal may be plotted against analyteconcentration and a best fit line may be generated between the datapoints. The best fit line may, in some cases, obey the equation y=mx+b,where y is the signal measured, m is the sensitivity (i.e., the slope ofthe line), x is analyte concentration, and b is a constant attributableto background. Once a best fit line is generated, unknown analyteconcentrations can be determined using the equation. In some systems,the relationship between analyte concentration and signal measured maybe linear or approximately linear within particular ranges of analyteconcentration. The region where measured signal has a linearrelationship to analyte concentration is referred to as the “linearrange” herein. In some cases, the linear range may extend between thesystem's limit of detection (LOD) and the limit of linearity (LOL).Below the LOD, signal measured may be attributable to backgroundinterference and above the LOL, signal measured has a non-linearrelationship to analyte concentration. Accordingly, measurementsobtained between the LOD and the LOL (in the linear range) may produce amore reliable calibration curve than values outside the linear range.

As previously described, the disclosed devices include a calibrationstrip with particular analyte concentrations selected to produce signalsto generate a reliable calibration curve to quantify analyteconcentration in a solution that is applied to the sample strip. In someembodiments, the disclosed calibration strip includes at least onenon-zero analyte concentration value. In these and other embodiments,the calibration strip may include a region with an analyte concentrationof zero, from which signal is measured and then used to generate thecalibration curve. In some particular example embodiments, only twosignals read from the calibration strip (one from a region with anon-zero analyte concentration and another from a region with an analyteconcentration of zero) may be used to generate a calibration curve. Insome such example embodiments, the non-zero analyte concentration may beselected to be within the linear range to maximize accuracy. In theseand other embodiments, the measured signal in a region with an analyteconcentration of zero would correspond to the value of the “b” variablein the best fit line equation and would indicate signal produced frombackground and non-specific binding. Measuring signal from a region withan analyte concentration of zero may also be used in various embodimentsto provide additional safety controls. For example, visual colordeveloping in a region with zero analyte concentration may indicate atest failure and/or inaccuracy of results. Numerous configurations andvariations will be apparent to those skilled in the art uponconsideration of the subject dislcosure.

The disclosed cassettes may be compatible with an instrument capable ofinterpreting images either through light transmission or lightreflectance. In some embodiments, a cassette may be read using lightreflection and transmission-based detection methods. In embodimentswhere increased sensitivity is desired, light transmission can be used.

In some embodiments, the sample analysis results can be providedquantitatively. However, it is to be understood that in someembodiments, the quantitative results may be reported qualitatively, ifdesired. For example, in the case of TSH measurements, results may bereported as EUTHYROID, HYPERTHYROID, or HYPOTHYROID.

The disclosed methods may be used to monitor disease progression orregression with regard to medical treatment including prescriptions, insome embodiments. In some embodiments, the system may be used to monitorpatient compliance with prescribed medications.

In various embodiments, the signals that develop are in addition tocolloidal gold derived from nanomaterial-based Biosensors incorporatingvarious detector strategies such as fluorescent labels, enzymes,chemiluminescence chemistries, ferromagnetic particles and silicaparticles.

In some cases, the quantitative result may be reported as aconcentration of analyte mass per unit volume, an activity unit per unitvolume or as a percentage of a reference value.

The disclosed cassettes can provide uniformity of liquid flow on bothsample and calibration strips due to precision placement of pressurepoints within the device and suitable incorporation of barriers toensure that migration or flow is absolutely restricted to the membranestrips. The disclosed systems can also utilize light reflection ortransmission based detection with the same cassette and instrument. Forcertain tests such as a test for pregnancy where a number orquantitation is not required, the test can be read visually. In someembodiments, a wash port may be used to quantitate samples that featurehemolyzed whole blood or pigmented samples. The disclosed systems alsomay have the ability to remove interfering (false positives)particulates that may be present in certain samples by incorporatingsuitable membrane-based filters. The disclosed systems may also imageand record the volume of sample added to the device, (for example a dropof blood from a finger prick, which would eliminate the need foraccurate pipettes). Off-board mixing of colloidal gold and sample foradded sensitivity and flexibility may be used in any of the disclosedassay designs.

In some embodiments, multiple sample types may be tested by thedisclosed cassettes, including whole blood, urine, saliva, swabs, and/orfecal matter. With kinetic assay capability, the disclosed systems mayreport a result quickly (for example, within two to ten minutes),depending on sample concentration. The disclosed systems may have theability to perform nucleic acid (PCR, rtPCR) assays and/or the abilityto multiplex analytes on the same strip. The disclosed systems may alsobe compatible with colloidal gold, latex particles, fluorescent labelsand superparamagnetic particles. In some embodiments, the calibrationstrip may feature a lot-specific calibrator which is referenced to acalibration curve performed at the date of manufacturing.

The features and advantages described herein are not all-inclusive and,in particular, many additional features and advantages will be apparentto one of ordinary skill in the art in view of the drawings,specification, and claims. Moreover, it should be noted that thelanguage used in the specification has been selected principally forreadability and instructional purposes, and not to limit the scope ofthe inventive subject matter described herein. The foregoing descriptionof the embodiments of the disclosure has been presented for the purposeof illustration; it is not intended to be exhaustive or to limit theclaims to the precise forms disclosed. Persons skilled in the relevantart can appreciate that many modifications and variations are possiblein light of the above disclosure.

What is claimed is:
 1. A cassette comprising: a calibration stripcomprising a first region and a second region, the first region having afirst concentration of an analyte and the second region having a secondconcentration of the analyte, wherein the first concentration isdifferent from the second concentration; a sample strip positionedparallel to the calibration strip; a sample port in fluid communicationwith the sample strip; and a fluid port in fluid communication with thecalibration strip and the sample strip.
 2. The cassette of claim 1,wherein the calibration strip further comprises a binding partner forthe analyte in the first region and in the second region.
 3. Thecassette of claim 1, wherein the calibration strip further comprises aconjugate pad comprising a marker configured to bind with the analyte ora binding partner.
 4. The cassette of claim 1, wherein the calibrationstrip further comprises a marker bound to or configured to bind to theanalyte in the first region and in the second region.
 5. The cassette ofclaim 4, wherein the calibration strip further comprises a conjugate padcomprising a binding partner for the analyte and/or the marker.
 6. Thecassette of claim 1, wherein the calibration strip further comprises athird region having a third concentration of the analyte that isdistinct from the first concentration and the second concentration. 7.The cassette of claim 1, further comprising a wash port in fluidcommunication with the sample strip.
 8. The cassette of claim 1, whereinthe sample strip further comprises a control line comprising a knownconcentration of an analyte different from the analyte of interest and atest line comprising a binding partner for an analyte of interest. 9.The cassette of claim 1, wherein the first concentration of the analyteis zero and the second concentration of the analyte is greater thanzero.
 10. The cassette of claim 1, wherein the first concentration ofthe analyte is greater than zero and the second concentration of theanalyte is greater than zero.
 11. The cassette of claim 1, wherein theanalyte of interest is a receptor, an antigen, an antibody, a hormone, aprotein, an enzyme, DNA, RNA, a pharmaceutical substance, or anenvironmental pollutant.
 12. The cassette of claim 1 further comprisinga housing inside which the calibration strip and the sample strip arefixedly stored, wherein the housing contacts the sample strip in atleast two locations and contacts the calibration strip in at least twolocations.
 13. The cassette of claim 12, wherein the housing contactsthe sample strip in at least four locations and contacts the calibrationstrip in at least four locations.
 14. A cassette comprising: asubstantially rigid housing comprising a top portion and a bottomportion; a calibration strip fixedly retained in the housing, thecalibration strip comprising a first region and a second region, thefirst region having a first concentration of an analyte and the secondregion having a second concentration of the analyte, wherein the firstconcentration is different from the second concentration; a sample stripfixedly retained in the housing; a sample port formed in the top portionof the housing above the sample strip; and a fluid port formed in thetop portion of the housing above both the calibration strip and thesample strip.
 15. The cassette of claim 14, wherein the top portion ofthe housing further comprises a wash port formed in the top portion ofthe housing providing access to the sample strip.
 16. The cassette ofclaim 14, wherein the bottom portion of the housing includes a samplevolume analysis port underneath the sample strip or the sample port. 17.The cassette of claim 14, wherein the bottom portion of the housingincludes a flow strip light guide port positioned underneath the samplestrip and the calibration strip.
 18. The cassette of claim 14, whereinthe top portion of the housing includes a plurality of pressure points,wherein at least two pressure points are in contact with the samplestrip and at least two pressure points are in contact with thecalibration strip.
 19. The cassette of claim 14 further comprising aplurality of excess fluid channels formed in the bottom portion of thehousing, wherein one or more of the excess fluid channels are in fluidcommunication with the sample strip.
 20. The cassette of claim 19,wherein one or more of the excess fluid channels are in fluidcommunication with the calibration strip.
 21. A method of measuring theconcentration of an analyte in a sample, the method comprising:introducing the sample into a cassette having a calibration strip and asample strip; introducing a fluid to the calibration strip and thesample strip; optically detecting at least two signals from thecalibration strip; generating a calibration curve from the at least twosignals; detecting a signal from the sample strip; and determining aquantitative measurement of the concentration of the analyte in thesample based on the signal from the sample strip and the signals fromthe calibration curve.
 22. The method of claim 21, wherein the signalsfrom the calibration strip are detected using light transmission orlight reflectance.
 23. The method of claim 21, wherein the signal fromthe sample strip is detected using light transmission or lightreflectance.
 24. The method of claim 21, wherein the fluid is introducedto the calibration strip and the sample strip simultaneously.
 25. Themethod of claim 21, wherein the signal from the sample strip isoptically detected within ten minutes after the fluid is introduced. 26.The method of claim 21, wherein the quantitative measurement of theanalyte concentration in the sample has an error percentage of between1% and 10%.
 27. The method of claim 21, wherein the method is used tomonitor efficacy of drug therapy and/or patient compliance with respectto physician-prescribed medication in a point of care (POC) setting. 28.The method of claim 21, wherein the at least two signals opticallydetected from the calibration strip are produced from regions having anon-zero analyte concentration.
 29. The method of claim 21, wherein atleast one of the signals optically detected from the calibration stripis produced from a region having an analyte concentration of zero.